DDSM and Applications

In this chapter, we review the principles of delta-sigma modulation. We classify Delta-Sigma Modulators (DSMs) based on the types of signals they process and describe applications for each. Digital DSMs (DDSM) are used in fractional-N frequency synthesizers and oversampling Digital-to-Analog Converters (DACs). We review the basic operation of a delta-sigma DAC. Then we give an introduction to fractional-N synthesizers and the use of delta-sigma modulation in these systems. We highlight the problem of spurious tones in DDSMs resulting from short cycle lengths and indicate how they degrade the performance of the synthesizers. The chapter provides Simulink models and Matlab code for MASH, Multi-bit EFM and multi-bit SQ DDSMs.